A. Field of the Invention
This invention relates to rotating shaft multi-sensing. More specifically, the invention relates to an improved apparatus and method for measuring the physical parameters of a rotating shaft and communicating those parameters and other information to a stationary device.
B. Problems in the Art
Rotating shafts have numerous applications including drive shafts, as hydrostatic pump inputs and as motor outputs. In systems using rotating shafts, there is a rotor section and a stator section. The rotor section rotates and the stator section provides a stationary frame of reference with respect to the rotor section.
In such a system, it is desirable to measure the physical parameters of the rotating shaft for monitoring and other purposes. Such physical parameters include, but are not limited to rotational position, speed, velocity, acceleration, torque or side-loading, temperature, and vibration. These physical parameters can be measured with various sensors or calculated from other measurements.
There is a problem, however, in obtaining these physical parameters when the shaft is rotating, and in particular, when the shaft is rotating a continuous and full 360 degrees. The problem is communicating these parameters from the rotating shaft to the stator section.
A number of methods have been used in attempts to measure physical parameters of a rotating shaft. One such method is the use of a resolver. Resolvers have been used to sense angular position. Resolvers, however, require an oscillator and demodulator circuit with access to both the stator and rotor windings. This access meaning a wired connection. Thus, there are inherent difficulties with providing this wired access. Full 360 degree or continuous rotation could be provided for a resolver through use of a slip ring, also known as a rotary electrical joint. A resolver and slip ring combination however, adds cost and reduces reliability of the system.
Another class of device that has been used for angular position or speed sensing involves magnetometry related approaches. These approaches include Hall effect, magneto-restrictive, giant magneto-restrictive and similar approaches. One deficiency in these types of sensors is that they do not cover a continuous range of rotation. Furthermore, a magnetic field is required. Thus, a magnet or ring is required.
Optical sensors provide another approach. For example, optical encoders can be used to sense relative or absolute position. The use of optical sensors, however, is difficult and limited in demanding environments where dirt or dust negatively affect sensor performance.
A further problem in the prior art is that in order to obtain different types of sensing data different approaches may need to be combined.
It is therefore an objective of the present invention to provide an apparatus and method of measuring physical parameters of a rotating shaft and making those parameters available to a stationary device.
It is a further objective of the present invention to provide an apparatus and method of measuring physical parameters of a rotating shaft and making those parameters available to a stationary device while still permitting continuous rotation of the shaft.
It is a still further objective of the present invention to provide a contactless connection between the stator and rotor over which both power and data may be transferred.
Another objective of the present invention is to permit full operation even when the shaft is not rotating.
Yet another objective of the present invention is to provide a device that does not add significant weight or moment of inertia to the shaft.
Another objective of the present invention is to implement the device in a manner suitable for high volume production including high reliability and low cost.
These and other objectives will become apparent from the following description.
The following invention describes a method and means for sensing physical parameters of a shaft that is capable of continuous rotation and communicating those physical parameters to a stationary frame of reference. The invention provides for a number of different types of data to be sensed including rotational speed, rotational position, acceleration, torque, temperature, or vibration. Optionally, information can be digitally processed on the rotor. The invention also provides a contactless means of providing power to the rotor circuitry.